Scroll fans, also known as radial or centrifugal fans, are used in a variety of devices and for a variety of purposes. Applications include, for example, climate control, vehicle and machinery cooling systems, personal comfort, ventilation, fume extraction, removing dust, and drying. Specifically, scroll fans may be used in any number of devices ranging from hair dryers and leaf blowers to cooling units for personal computers and powered air purifying respirators.
A typical scroll fan has a scroll-shaped casing and a moving component, called an impeller. The impeller often consists of a central shaft about which a set of blades or ribs are positioned. Air typically enters the fan in or near the shaft. It then moves from the shaft to the opening in the scroll-shaped fan casing as the impeller is rotated. The air is spun outwards to the outlet by deflection and centrifugal force. Scroll fans blow air out at an angle that is oblique or perpendicular to the intake of the fan. Scroll fans can produce more pressure for a given air volume than other types of fans, which can be desirable for particular applications, such as those mentioned above.
In addition to a scroll-shaped casing and an impeller, scroll fans also typically include a motor, and often control circuitry. A traditional scroll fan construction has a scroll casing, an impeller enclosed within the scroll casing, a motor to rotate the impeller, and often a small printed circuit board (PCB) mounted within the motor. The motor and PCB can then be connected via a connector ribbon or other means to a larger printed circuit board. The scroll and larger PCB are then housed within their specific device.
Space can be an important constraining factor for any scroll fan design. Powered air purifying respirators (PAPR) are no exception. PAPR's containing scroll fans can come in a variety of designs including hoods, helmets, face masks, suits, belt mounted respirators and other forms. In many of these designs, particularly where the PAPR is intended to be portable or transported by the wearer, creating an lightweight, ergonomic, and compact design is particularly important.